数字在排序数组中出现的次数

public class 面试题38_数字在排列数组中出现的次数 {
	/*
	 * 题目描述
		统计一个数字在排序数组中出现的次数。

	 */
	public static void main(String[] args) {
		int[] a={1,2,2,3,3,3,3,4,5};
		int[] b={};
		//System.out.println(getLastK(a, 2, 0, 7));
		//System.out.println(getFirstK(b, 10, 0, 0));
		System.out.println(getTimesInNum(b,2));
	}
	public static int getTimesInNum(int[] a,int k){
		if(a==null||a.length==0){
			return 0;
		}
		int count=0;
		int first=getFirstK(a, k, 0, a.length-1);
		int last=getLastK(a, k, 0, a.length-1);
		if(first>-1&&last>-1){
			count=last-first+1;
		}
		return count;
	}
	public static int getLastK(int[] a,int k,int start ,int end){
		if(a==null||a.length==0||start>end){
			return -1;
		}
		int middleIndex=(start+end)/2;
		if(a[middleIndex]==k){
			if(middleIndex==a.length-1||a[middleIndex+1]!=k){
				return middleIndex;
			}else{
				start=middleIndex+1;
			}
		}else if(a[middleIndex]>k){
			end=middleIndex-1;
		}else{
			start=middleIndex+1;
		}
		return getLastK(a, k, start, end);
	}

	public static int getFirstK(int[] a,int k,int start ,int end){
		if(a==null||a.length==0||start>end){
			return -1;
		}
		int middleIndex=(start+end)/2;
		if(a[middleIndex]==k){
			if(middleIndex==0||a[middleIndex-1]!=k){
				return middleIndex;
			}else{
				end=middleIndex-1;
			}
		}else if(a[middleIndex]>k){
			end=middleIndex-1;
		}else{
			start=middleIndex+1;
		}
		
		return getFirstK(a, k, start, end);
	}
}